Bonding of metal carbonyl deposits



Patented Sept. 29, 1953 comma or, METAL e m DEPOSITS lb 0. F Dayton, 9 e assigns?! to he Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio No Drawing. Application April 6, 1949, Serial No..85,942

metals, and particularly with a method based on the decomposition of gaseous metal earbonyls.

This application is a continuation in part of my co-pending application, Serial No. 665,318, filed April 26, 1946, now Patent No. 2,475,601, issued July 12, 1949, entitled "Bonding of Metal Carbonyl Deposits.

In coatings obtained from metal carbonyls, the disadvantage heretofore has frequently been encountered of the coating not sufiiciently adhering to the base metal. Moreover, the metal coating would become blistered if the object so coated was raised to elevated temperatures, for example, in a heat treatment process.

It is an object of this invention to provide a method by which the above mentioned disadvantages are overcome.

'In particular, it is an object of this invention to provide a method for metal plating by which a firmly adhering metal coating is obtained.

It is another object of this invention to provide a method of producing metal coating which can withstand elevated temperatures without blistering. 1 I

It is still another object of this invention to provide a method of producing metal coatings which may be subjected to a heat-treatment process without thereby impairing the adherence of the coating. I

It is still another object of this invention to provide a product whose base material is provided with a uniform deposited coat consisting of two separately deposited layers.

These and other objects are accomplished'by carrying out the metal deposition in two stages in between which the base metal and. its coating are subjected to a de-gasification treatment carried out by subjecting the material to heat.

In the first or initial step, only. a very thin porous film is applied to the metallic baseby decomposing gaseous metal carbonyl. A layer 0f 0,000.01" to 0.90025", preferably of 0.00005 to 0.0.0015" in depth, was found most satisfactory for this initial coating. However, the invention is not. restricted to this particular ran e.

Afterthis first layer has been applied, the coated article is heat treated. While applicant does not wish to be bound by theory, it is believed that the heat-treatment step effects desorption of gas while the coating is still in a porous state. l

Since the porosity of a coating varies inversely as to thickness, and since heat treatment of thick coatings applied at one time blisters and 6 Claims. (Cl-1.17.165).

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n add ion t eas meta -brid fi ms mus be m ed fr m efits Such as QQPEH at. a umin m- This l may i re v d int e cl an by co tact. itlii he p ati chamber wit r du i g gases, I exam le. anaemia: t introduction of decomposable carbonyl "gases.

Inasmuch as identical cleaning steps have been used for identical bases which have been coated in one step and by the two step method of this invention, the pre-coating cleaning is- -not accountable for the difference 'inthe adhering character of the deposit k Gases maybe d'esorbedfrom the thinly coated bases by heating to a temperature in the range of 500 F.to 1200 F. depending uponthe temperature which can be applied to thebase withoutsoftening or destroying some characteristic such as temper orcan' be applied to the coating.

For example lead patterns should not beneated much above 550 F. while, on'the other hand, alloy steels withstand temperatures in excess of 1200* F. At thelower temperatures the'heating is continued for a longer time in order to eifect, comparative completeness of desorption. Heating periods'of -2/to 30 minutes have been found to be satisfactory. When heatlnga'copper base covered with an initial coating of nickel, a treatment-at atemperature of 80.0 to 900 F. for about 15 minutes was found mostv advantageogfi I The inte me ate heatrtreatmen may be 9%!- out n a hamber und r e n ox iz na bu n eterabl unde educing atmosphere caesitions. Nitrogen, carbon monoxide, carbon di oxide, hydrogen, natural gas, commercial brazing furnace gas or mixtures of the above gases or other gases known in the art are suitable for this purpose.

One of the features of well bonded coatings is their ability to withstand compression and expansion without breaking free from the base. Thus, any metal base which will withstand gas desorbing temperatures may be coated by this carbonyl decomposition process.

Base materials which may be coated are, for example, copper, aluminum, lead, cast iron, alloy steels, low carbon steels, non-ferrous alloys, such as bronze, brass, magnesium, and the like.

The process of this invention is applicable for plating with all metals which form gaseous carbonyls. Thus, plating with chromium, iron, tungsten, cobalt, molybdenum, tellurium, rhenium, and other metals may be successfully carried out by the method described.

Each of these metal carbonyls has a temperature at which decomposition is complete. However, decomposition does take place slowly at lower temperatures. For this reason it is preferred that the carbonyl be brought into contact quickly with the base metal heated to a temperature in the optimum decomposition range for each material.

In the case of tungsten, nickel, chromium, iron, we prefer to utilize a temperature in the range of 350 F. to 425 F., although temperatures below and above this range may be utilized and still acapplied to the coating of various metal bases with a number of metals deposited from volatile metal carbonyls:

Example I A copper plate was first mechanically cleaned by sanding. Thereafter the copper metal was heated to approximately 375 F. in an atmos- 'phere containing approximately 1.4 percent by volume of nickel carbonyl and diluted with carbon dioxide gas. The rate of gas flow was approximately 4 l. per minute at a temperature of 78 F. and 125 mm. Hg. The copper was exposed to this atmosphere for about 2 minutes after which time a film of 0.00007" thickness had formed on the copper base. Thereafter the metal was heated in an atmosphere of natural gas to a temperature of about 800 F. for approximately minutes.

After these preliminary steps the coating proper was performed by subjecting the metal to the same conditions and gases as in the preliminary film-forming step. This second step was carried out for about 15 minutes when a coating of 0.0004 had formed.

In order to increase the ductility of the coating, I subjected the metal to an additional heating step. This step consisted in heating for 15 minutes to a temperature of from 800 to 900 F'. in an atmosphere of natural gas.

Example II A lead pattern may be coated in the equipment utilized in the plating operation of Example I.

The lead pattern may be coated with iron deposited from iron carbonyl. The base may be heated to approximately 360 F. in an atmosphere of nitrogen containing about 2 percent by volume of iron carbonyl. After exposure of the pattern to this atmosphere for about 2 minutes, the temperature of the pattern may be raised to 525 F. and held there for 20 minutes.

After these preliminary steps the final filmforming step may be performed under the same conditions as is maintained in the preliminary coating step.

Example III An aluminum radar antenna may be coated in the same equipment as is used in Examples I and II.

The aluminum may be treated with acid and then buffed to prepare clean surfaces. The aluminum may be coated with nickel by heating the base to approximately 375 F. in one minute with a feed rate of approximately 50 cubic feet per hour of nickel carbonyl vapor diluted with hydrogen.

The initially coated base may be heat treated at 750 F. for 20 minutes to desorb gas. Following the heat treatment, the final coating and heat treating may follow exactly the pattern of Example I.

Example IV An SAE 1020 steel plate may be treated under similar conditions to Example I to plate the steel base with chromium deposited at a temperature of about 400 F.

The coatings obtained by the process of this invention on each of the bases of the examples are uniform in structure, free from blisters, and well adhering to the base metal. Heat treatment does not form blisters and impair the firm bond between the coating and the base metal.

In addition, apparatus such as the radar antenna of Example III, have been subjected to special tests under which the base suffered a 15 percent elongation and withstood tensile strain of 90,000 pounds per square inch before breaking. Up to the breaking point, the adhering coating of nickel exhibited no checking or breaking tendency and the coating parted in line with the point of failure of the base material.

It will be understood that this invention is not to be restricted to the examples given in the specification, but that it is susceptible to various modifications and changes which come within 'the spirit of the disclosure and the scope of the appended claims.

to 400 F. with a stream of gaseous nickel carbonyl diluted with a non-oxidizing gas, thereafter heating said thinly coated base to a temperature in the range of 500 F. to 1200 F. while maintaining an atmosphere of CO2 about the heated aluminum base, and then exposing said nickel coated aluminum base to nickel carbonyl gas While said base is heated to a temperature high enough to decompose said carbonyl gas and deposit a coating of nickel of the desired thickness.

2. In a process for depositing a firmly adhering metal coating on a base material by the deposition of metal from a heat-decomposable gaseous metal compound, the steps comprising subjecting said material to an initial coating of metal by contacting the same with a heat-decomposable gaseous metal compound at a temperature causing decomposition of said gaseous metal compound and deposition of a relatively thin metal coating thereon and between about 0.00001 and 0.00025 inch in thickness, subjecting the resultant coated product to a heat treatment which comprises heating said thinly coated material in a non-oxidizing atmosphere to a temperature substantially above the decomposition temperature point of said gaseous metal compound, and depositing a metal coating thereover by exposing the resultant heat-treated thinly coated material to a heat-decomposable gaseous metal compound at a temperature causing decomposition of said last mentioned gaseous metal compound and deposition of the metal constituent thereof on said heat-treated coated material.

3. In a process for depositing a firmly adhering metal coating on a metal base by decomposing and depositing metal from a heat-decomposable gaseous metal compound, the steps comprising initially coating said metal base by contacting the same with a heat-decomposable gaseous metal compound at a temperature causing decomposition of said gaseous metal compound and deposition of a relatively thin coating of metal thereon on the order of 0.00001 to 0.00025 inch in thickness, heating said thinly coated metal base to a temperature between about 500 F. and 1200 F. while maintaining said material in a non-oxidizing atmosphere, and thereafter depositing a relatively thick metal coating thereover by exposing the resultant heat-treated thinly coated metal base material to a heat-decomposable gaseous metal compound at a temperature causing decomposition of said last mentioned gaseou metal compound and deposition of the metal constituent thereof on said heattreated coated metal base material.

4. In a process for depositing a firmly adhering metal coating on a base material by the deposition of metal from a heat-decomposable gaseous metal compound, the steps comprising subjecting said material to an initial coating of metal by contacting the same with a heat-decomposable gaseous metal compound at a temperature causing decomposition of said gaseous metal compound and deposition of the metal constituent thereof as a relatively thin coating thereon and between about 0.00001 and 0.00025 inches in thickness, said heat-decomposable gaseous metal compound being selected from the group consisting of the carbonyls of nickel, chromium, iron, tungsten, cobalt, molybdenum, tellurium and rhenium, subjecting the resultant coated product to a heat treatment which comprises heating said thinly coated material in a non-oxidizing atmosphere to a temperature substantially above the decomposition temperature point of said gaseous metal compound, and depositing a metal coating thereover by exposing the resultant heat-treated thinly coated material to a heat-decomposable gaseous metal compound at a temperature causing decomposition of said last mentioned gaseous metal compound and deposition of the metal constituent thereof on said heat-treated coated material, said last mentioned gaseous metal compound being selected from said group of carbonyls.

5. In a process for depositing a firmly adhering metal coating on an aluminum base material by the deposition of metal from a heat-decomposable gaseous metal compound, the steps comprising subjecting said material to an initial coating of metal by contacting the same with a heat-decomposable gaseous metal compound at a temperature causing decomposition of said gaseous metal compound and deposition of a relatively thin metal coating thereon and between about 0.00001 to 0.00025 inch in thickness, said heat-decomposable gaseous metal compound being selected from the group consisting of the carbonyls of nickel, chromium, iron, tungsten, cobalt, molybdenum, tellurium and rhenium, subjecting the resultant coated product to a heat treatment which comprises heating said thinly coated material in a non-oxidizing atmosphere to a temperature substantially above the decomposition temperature point of said gaseous metal compound, and depositing a metal coating thereover by exposing the resultant heat-treated thinly coated aluminum base material to a heatdecomposable gaseous metal compound at a temperature causing decomposition of said last mentioned gaseous metal compound and deposition of the metal constituent thereof on said coated material.

6. In a process for depositing a firmly adhering metal coating of predetermined thickness by the decomposition of nickel carbonyl on an aluminum base, the steps comprising first applying a thin coating on the order of 0.00001 to 0.00025 inch in thickness of nickel on the clean metal base by contacting the aluminum base while heated to a temperature in the range of 375 F. to 400 F with a stream of gaseous nickel carbonyl diluted with a non-oxidizing gas to cause decomposition of said nickel carbonyl and the deposition of nickel on said aluminum base,

heat treating the resultant nickel coated product by heating said thinly coated base to a temperature in the range of 500 F. to 1200 F. while maintaining an atmosphere of CO2 about the heated aluminum base to prevent oxidation of the metal, and then exposing the resultant heattreated nickel coated aluminum base to nickel carbonyl gas while said base is heated to a temperature high enough to decompose said carbonyl gas and deposit on said heat-treated aluminum base a coating of nickel of the desired thickness.

ALBERT O. FINK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,515,658 Cole NOV. 18, 1924 1,752,239 Ferranti Mar. 25, 1930 2,063,596 Feiler Dec. 8, 1936 2,304,182 Lang Dec. 8, 1942 2,332,309 Drummond Oct. 19, 1943 2,475,601 Fink July 12, 1949 FOREIGN PATENTS Number Country Date 487,854 Great Britain Sept. 22, 1936 

1. IN A PROCESS FOR DEPOSITING A FIRMLY ADHERING METAL COATING OF PREDETERMINED THICKNESS BY THE DECOMPOSITION OF NICKEL CARBONYL ON AN ALUMINUM BASE, THE STEPS COMPRISING FIRST APPLYING A THIN POROUS NICKEL FILM TO THE CLEAN METAL BASE TO A DEPTH OF BETWEEN ABOUT 0.00005 INCH TO 0.00015 INCH BY CONTACTING THE ALUMINUM BASE HEATED TO A TEMPERATURE IN THE RANGE NICKEL CARTO 400* F. WITH A STREAM OF GASEOUS NICKEL CARBONYL DILUTED WITH A NON-OXIDIZING GAS, THEREAFTER HEATING SAID THINLY COATED BASE TO A TEMPERATURE IN THE RANGE OF 500* F. TO 1200* F. WHILE MAINTAINING AN ATMOSPHERE OF CO2 ABOUT THE HEATED ALUMINUM BASE, AND THEN EXPOSING SAID NICKEL COATED ALUMINUM BASE TO NICKEL CARBONYL GAS WHILE SAID BASE IS HEATED TO A TEMPARATURE HIGH ENOUGH TO DECOMPOSE SAID CARBONYL GAS AND DEPOSIT A COATING OF NICKEL OF THE DESIRED THICKNESS. 